Biochemically adaptive materials based on (iso)thermally-responsive polymers

The ability to programme and manipulate small changes at the molecular level to elicit a dramatically enhanced macroscopic response makes “stimuli-responsive” materials a fascinating topic of study. This work seeks to manipulate the solubility switch associated with polymers exhibiting a Lower Critical Solution Temperature without a temperature change (‘isothermally’). This concept, as overviewed in Chapter 1, has attractive applications in biological settings where variations in in vivo microenvironments may be used to produce increasingly targeted delivery vehicles, and to mediate cell membrane interactions. Using controlled radical polymerisation, pre-designed backbones, end-group(s) or side-chains can be targeted to control the hydrophilic-hydrophobic balance of a thermo-responsive system. Chapters 2 and 3 investigate this concept, using the chemical reduction of a functional polymer backbone or end-group to trigger isothermal polymer precipitation or solubilisation in linear and nanoparticle systems respectively. Chapter 4 applies a metal-ligand binding motif, prevalent in bacteria, to end-functional polymers as an alternative means of promoting isothermal polymer precipitation. This binding motif is then transferred to a nanoparticle system in Chapter 5, and used for the first time to prepare an optical, particle-based biosensor for the detection of physiologically relevant iron concentrations. Finally, Chapter 6 describes the enzymatic degradation of a polymer side-chain as a means of triggering isothermal precipitation and considers its potential to mediate cellular uptake. In summary, a series of functionalised polymers and nanoparticles have been synthesised and their (isothermal) responses characterised. These materials may have exciting potential in the emerging field of nanomedicine.